1. Technical Field
Generally, the present invention relates to mixers, and more specifically to a mixer of the so-called rotator-stator type that includes a stator having a plurality of openings or holes and a rotor that is disposed on the inner side of the stator and spaced by a particular gap away from the stator.
2. Background
As shown in FIG. 1, it is general that the mixer of the so-called rotor-stator type generally comprises a mixer unit 4 that includes a stator 2 having a plurality of openings (holes) 1 and a rotor 3 disposed on the inner side of the stator 2 and spaced by a particular gap δ from the stator 2. Such mixer of the rotor-stator type is provided for subjecting a fluid being processed to the emulsification, dispersion, particle size breakup, mixing or any other similar process, by taking advantage of the fact that a high shear stress may be produced in the neighborhood of a gap between the stator 3 rotating at high-speeds and the fixed stator 2. This mixer is used for mixing or preparing the fluid being processed, and has a wide variety of applications in which foods, pharmaceutical medicines, chemical products and others can be manufactured.
The mixer of the rotor-stator type may be classed according to the type of the circulation mode for the fluid being processed, that is, one being the externally circulated mixer in which the fluid liquid being processed may be circulated in the direction indicated by the arrow 5a in FIG. 2, and the other being the internally circulated mixer in which a liquid being processed may be circulated in the direction indicated by the arrow 5b in FIG. 2.
For the mixers of the rotor-stator type, many different configurations and circulation modes or systems have been proposed. For example, there is the Japanese patent application No. 2005-506174 in which the mixer of the rotor-stator type and the particle size breakup method are proposed, in which the mixer includes a stator having a plurality of openings (holes) and a rotor disposed on the inner side of the stator and spaced by a specific gap away from the stator. It is disclosed that the mixer may be used widely in the fields in the pharmaceutical medicines, nutrition supplement foods, other foods, chemical products, cosmetics and the like can be manufactured. It is also disclosed that the method disclosed enables the scale up function to be performed in the efficient, simple and easy manner.
In addition, for those past years, several indices (theories) have been reported as the performance estimation method for the mixers having the different configurations.
Not only for the mixer of the rotor-stator type as described above but also for all other type mixers, it is reported that, when the liquid-liquid dispersion operation in particular occurs, for example, the drop diameter size can be discussed in terms of the magnitude (smallness or greatness) of the values that can be obtained by calculating the average energy dissipation rate (Publications 1 and 2). In those publications 1 and 2, however, the method for calculating the average energy dissipation rates is not disclosed specifically.
The publications 3 to 6 report several study cases that may be applied to each individual mixer and in which the results obtained by the respective experiments have been organized into the tabular forms. In those study cases (Publications 3 to 6), however, it is considered that the mixer's particle size breakup function is only affected by the gap between the rotor and stator and by the openings (holes) on the stator. Only the information that is different for each different type mixer is reported.
Several study cases are reported (Publications 7 and 8), in which the particle size breakup mechanism for the mixer of the rotor-stator type was considered and discussed. In those publications 7 and 8, it is suggested that the energy dissipation rates of the turbulent flow will contribute to the particle size breakup effect, and the particle size breakup effect may be affected by the frequency (shear frequency) of the turbulent flow with which the particle size breakup effect is placed under the shear stress of the fluid being processed.
For the scale-up method for the mixer of the rotor-stator type, there are several reports (Publication 8) in which the final drop diameter (maximum stable drop diameter) can be obtained during the long-time mixer running period. This, however, is not practical in the actual production sites and is of no utility. Specifically, there are no reports regarding the study cases in which the processing (agitation and mixing) time of the mixer is the object for consideration, and those study cases are not useful enough to estimate the drop diameters that can be obtained during the particular mixer running period. Although it is reported that the drop diameters may be estimated by considering the mixer processing time, yet only the phenomenon (factual action) that is based on the actual measured values (experimental values) is reported. There are no study cases in which such phenomenon is analyzed theoretically.
The following publication, which is the document related to the patent application, is cited herein for reference:                Japanese Patent Application No. 2005-506174        
The following publications, which are not related to the patent application, are cited herein for reference:    (1) David, J. T.; “Drop Sizes of Emulsions Related to Turbulent Energy Dissipation Rates”, Chem. Eng. Sci., 40, 839-842 (1985) and David J. T.; “A Physical Interpretation of Drop Sizes in Homogenizers;    (2) Agitated Tanks, Including the Dispersion of Viscous Oils”, Chem. Eng. Sci., 42, 1671-1676 (1987);    (3) Calabrese, R. V., M. K. Francis, V. P. Mishra and S. Phongikaroon; “Measurement and Analysis of Drop Size in Batch Rotor-Stator Mixer”, Proc. 10th European Conference on Mixing, pp. 149-156, Delft, the Netherlands (2000);    (4) Calabrese, R. V., M. K. Francis, V. P. Mishra, G. A. Padron and S. Phongikaroon; “Fluid Dynamic and Emulsification in High Shear Mixers”, Proc. 3rd World Congress on Emulsion, pp. 1-10, Lyon, France (2002);    (5) Maa, Y. F., and C. Hsu, and C. Hsu; “Liquid-Liquid Emulsification by Rotor/Stator Homogenization”, J. Controlled. Release, 38, 219-228 (1996);    (6) Barailler, F., M. Heniche and P. A. Tanguy; “CFD Analysis of a Rotor-Stator Mixer with Viscous Fluids”, Chem. Eng. Sci., 61, 2888-2894 (2006);    (7) Utomo, A. T., M. Baker and A. W. Pacek; “Flow Pattern, Periodicity and Energy Dissipation in a Batch Rotor-Stator Mixer”, Chem. Eng. Res. Des., 86, 1397-1409 (2008);    (8) Porcelli, J.; “The Science of Rotor-Stator Mixers”, Food Process, 63, 60-66 (2002);    (9) Urban, K.: “Rotor-Stator and Disc System for Emulsification Processes”, Chem. Eng. Technol., 29, 24-31 (2006)